Pollen pool heterogeneity, which violates an assumption
of the mixed-mating model, is one of the major problems
facing population geneticists concerned with measuring
plant mating systems. In the present study, isozyme markers
were used to examine pollen pool heterogeneity in two
natural populations of jack pine, Pinus banksiana Lamb.,in
northwestern Ontario, Canada. Population multilocus
estimates of outcrossing rate ranged from 0.829 to 0.952
and differed significantly between populations. Singletree
outcrossing rates were found to be homogeneous among
trees in both populations. Computer simulation studies
shoved that the consanguineous mating pollen pool was a
potentially important component of the pollen pool, capable
of biasing population outcrossing estimates downward. In
contrast, random heterogeneity of the pollen pool was found
to have no effect on population estimates of outcrossing
rates. Pollen pool heterogeneity existed in these two
natural populations. However, it appeared to be random in
nature and therefore did not affect the population
outcrossing estimates.